Travel control device, vehicle, and travel control method

ABSTRACT

Provided are a travel control device, a vehicle, and a travel control method that ensure safety in cases of a possible lane departure. This travel control device is equipped with: a travel control unit that switches between and executes a constant speed travel control for causing a vehicle 1 to travel at a target speed and a coasting control for causing the vehicle to travel by inertia; and a switching control unit that, in cases in which it has been determined by a lane departure warning unit that there is a risk that the vehicle will depart from the travel lane while executing the constant speed travel control or the coasting control, controls the travel control unit to execute the constant speed travel control without executing the coasting control for a prescribed period of time.

RELATED APPLICATIONS

This application is a National Phase of PCT Patent Application No.PCT/JP2018/010555 having International filing date of Mar. 16, 2018,which claims the benefit of priority of Japanese Patent Application No.2017-056555 filed on Mar. 22, 2017. The contents of the aboveapplications are all incorporated by reference as if fully set forthherein in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

This disclosure relates to a travel control device for controlling thetravel of a vehicle, a vehicle, and a travelling control method.

Conventionally, there is known a travel control device which controlsthe automatic traveling of a vehicle (traveling without requiring thedriver's operation).

For example, Patent Literature 1 discloses a travel control device thatperforms a control (hereinafter referred to as a constant velocitytraveling control) in which the vehicle velocity is maintained at a setvelocity (hereinafter referred to as the target vehicle velocity) to runthe vehicle.

For example, in Patent Literature 2, there is disclosed a travel controldevice which performs a control for allowing the vehicle to travel byinertia (hereinafter referred to as coasting control) by temporarilystopping an engine and disconnecting a power transmission mechanismprovided in a power transmission system between a transmission and theengine or between the transmission and wheels when predeterminedconditions are satisfied while the vehicle is traveling.

Further, the lane departure warning system (LDWS) is known as atechnology for ensuring the safety of the traveling vehicle in therelated art (see, for example, PTL 3). The lane departure warning systemdetects the lane on the road where the vehicle is traveling, determineswhether the vehicle is likely to depart from the lane, and outputs analarm when there is a risk of departing the lane, and warns the driverof the vehicle.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Application Laid-Open No. 2017-024479

PTL 2: Japanese Patent Application Laid-Open No. 2006-200370

PTL 3: Japanese Patent Application Laid-Open No. 2013-003913

SUMMARY OF THE INVENTION Technical Problem

However, in a vehicle capable of switching between constant velocitytraveling and coasting, when the lane departure warning system isapplied, the following problems are posed because each control logic isdifferent.

For example, even when the lane departure warning system determines thatthere is a likelihood of lane departure during coasting, the coastingmay continue.

Further, for example, even when it is determined that the lane departurewarning system determines that there is likelihood of the lane departureduring constant velocity traveling, when the coasting starting conditionis satisfied, switching from the constant velocity traveling to thecoasting is performed.

As described above, if coasting is performed when there is likelihood oflane departure, the brake is not operated, so that it is very dangerous.

An object of this disclosure is to ensure safety in the case where thereis a risk of lane departure.

Solution to Problem

A travel control device according to one aspect of the presentdisclosure includes: a travel control section that switches between aconstant velocity traveling control for causing a vehicle to travel at atarget vehicle velocity and a coasting control for allowing the vehicleto travel by inertia, and a switching control section that controls thetravel control section to execute the constant velocity travelingcontrol without executing the coasting control when the vehicle islikely to depart from a traveling lane under the constant velocitytraveling control or the coasting control.

A vehicle according one aspect of the present disclosure includes thetravel control device according to the one aspect of the presentdisclosure.

A travel control method according to one aspect of the presentdisclosure is a method performed by a travel control device thatswitches between a constant velocity traveling control for causing avehicle to travel at a target vehicle velocity and a coasting controlfor allowing the vehicle to travel by inertia, the method including:executing the constant velocity traveling control without executing thecoasting control when the vehicle is likely to depart from the travelinglane under the constant velocity traveling control or the coastingcontrol.

Advantageous Effects of Invention

According to this disclosure, it is possible to ensure safety in thecase where there is likelihood of lane departure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an example of aconfiguration of a vehicle including a travel control device accordingto an embodiment of this disclosure;

FIG. 2 is a block diagram illustrating an example of a configuration ofa travel control device according to an embodiment of this disclosure;

FIG. 3 is a diagram illustrating an example of road gradient informationand a traveling schedule on a first road;

FIG. 4 is a diagram illustrating an example of road gradient informationand a traveling schedule on a second road; and

FIG. 5 is a flowchart illustrating an example of the operation of thetravel control device according to the embodiment of this disclosure.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

Hereinafter, embodiments of this disclosure will be described in detailwith reference to the drawings.

<Example of Configuration of Vehicle 1>

First, the configuration of vehicle 1 including travel control device100 according to the embodiment of this disclosure will be described.FIG. 1 is a block diagram illustrating an example of a configuration ofvehicle 1 including travel control device 100 according to the presentembodiment. Hereinafter, a description will be given of a portionrelated to travel control device 100, focusing on the parts associatedwith travel control device 100.

Vehicle 1 is a vehicle capable of switching between a constant velocitytraveling and a coasting. The constant velocity traveling (also referredto as driving travel) is a travel in which vehicle 1 is travelled todrive wheels 9 by a drive system to be described later to maintain thetarget vehicle velocity (target vehicle velocity V illustrated in FIGS.3 and 4). The coasting is traveling in which vehicle 1 is driven byusing the inertial force without driving wheels 9 by a drive systemdescribed later.

In the present embodiment, as an example, a case where coasting is aneutral inertia traveling (hereinafter referred to as “N coasting”) inwhich the gear stage of the transmission is neutral will be described asan example, but the present invention is not limited thereto, and thefree-run inertia traveling may also be used. While the N coasting isperformed by supplying the fuel to the engine in a state where theclutch in the power transmission path is disengaged and the engine isdisconnected from the wheels, the free-run inertia traveling isperformed by stopping the supply of fuel to the engine in a state wherethe clutch in the power transmission path is disengaged and the engineis disconnected from the wheels.

In the following description, control for causing vehicle 1 to executeconstant velocity traveling is referred to as “constant velocitytraveling control”, and control for causing vehicle 1 to execute the Ncoasting is referred to as “N coasting control”.

Vehicle 1 illustrated in FIG. 1 is a large vehicle such as a truck onwhich a series 6 cylinder diesel engine is mounted, for example.

As illustrated in FIG. 1, vehicle 1 includes engine 3, clutch 4,transmission 5, propulsion shaft (propeller shaft) 6, differentialdevice (differential gear) 7, drive shaft 8, and wheels 9 as aconfiguration of a drive system for traveling the vehicle.

Power of engine 3 is transmitted to transmission 5 via clutch 4, and thepower transmitted to transmission 5 is further transmitted to wheels 9via propulsion shaft 6, differential device 7, and drive shaft 8. Thus,power of engine 3 is transmitted to wheels 9, and vehicle 1 travels.

Further, vehicle 1 has braking device 40 as a structure of a brakingsystem for stopping the vehicle. Braking device 40 includes foot brake41 which imparts a resistance force to wheels 9, retarder 42 whichapplies a resistance force to propulsion shaft 6, and an exhaust brake43 which applies a load to the engine.

Further, vehicle 1 has automatic traveling device 2 as a configurationof a control system for controlling travel of vehicle 1. Automatictraveling device 2 is a device for causing vehicle 1 to perform anautomatic traveling (constant velocity traveling or coasting) bycontrolling the output of engine 3, the disengagement of clutch 4 andthe shift of transmission 5, and includes a plurality of controldevices.

Specifically, automatic traveling device 2 includes engine ECU (enginecontrol device) 10, power transmission ECU (power transmission controldevice) 11, target vehicle velocity setting device 13, increase/decreasevalue setting device 14, road information acquisition device 20, vehicleinformation acquisition device 30, and travel control device 100.

Engine ECU 10, power transmission ECU 11 and travel control device 100are connected to each other by an on-vehicle network, so that necessarydata and control signals can be transmitted to and received from eachother.

Engine ECU 10 controls the output of engine 3. Power transmission ECU 11controls the disengagement of clutch 4 and the shift of transmission 5.

Target vehicle velocity setting device 13 sets target vehicle velocity V(see FIG. 3 and FIG. 4) during the constant velocity traveling ofvehicle 1 to travel control device 100.

Increase/decrease value setting device 14 sets velocity decrease value−V1 and velocity increase value +V1 at the constant velocity travelingof vehicle 1 in travel control device 100. These values V, −V1 and +V1are parameters used for automatic travel of vehicle 1.

Target vehicle velocity setting device 13 and increase/decrease valuesetting device 14 include, for example, an information input interfacesuch as a display with a touch panel disposed on a dashboard (notillustrated) of a driver's seat, and receive the setting of theparameters from the driver. Target vehicle velocity V, velocity decreasevalue −V1, and velocity increase value +V1 are referred to as “settinginformation” as appropriate.

When vehicle 1 is likely to depart from the traveling lane (thetraveling lane indicating the boundary of the road on which vehicle 1 istraveling), output device 15 outputs an alarm for notifying the driverof the likelihood of lane departure (hereinafter simply referred to asan alarm) under the control of travel control device 100 (lane departurewarning section 140 illustrated in FIG. 2). Output device 15 mayinclude, for example, a display, a speaker, or both.

Road information acquisition device 20 acquires road informationindicating the road condition and the current position of vehicle 1, andoutputs the road information to travel control device 100. For example,road information acquisition device 20 includes current positionacquisition device 21 which is a receiver of a satellite positioningsystem (GPS), weather acquisition device 22 which acquires weatherduring traveling, ambient sensor 23 which detects a distance to avehicle traveling around vehicle 1 (such as a preceding vehicle and aparallel traveling vehicle) and a vehicle velocity difference, andimaging device 24 (for example, a CCD camera) which captures thesurroundings of vehicle 1.

It is preferable that the road information includes road gradientinformation indicating the gradient of each point of the road, inconsideration of the traveling schedule generated by travel controldevice 100 (travel control section 120 in FIG. 2). The road gradientinformation is data describing the altitude (road altitude) of thecorresponding positions in association with the horizontal positions(latitude/longitude information or the like) of each road.

Vehicle information acquisition device 30 acquires vehicle informationindicating the operation contents of the driver and the state of vehicle1 and outputs the vehicle information to travel control device 100. Forexample, vehicle information acquisition device 30 includes: acceleratorsensor 31 configured to detect a depression amount of an acceleratorpedal; brake switch 32 for detecting whether or not a brake pedal isdepressed; shift lever 33; turn signal switch 34; and vehicle velocitysensor 35 for detecting the velocity of vehicle 1.

Travel control device 100 generates a traveling schedule includingconstant velocity traveling and N coasting based on the settinginformation, road information, and vehicle information described above.

Then, travel control device 100 controls each part of vehicle 1 so thatvehicle 1 travels in accordance with the generated traveling schedule.

Travel control device 100 detects a traveling lane of a road on whichvehicle 1 is traveling based on an image photographed by imaging device24. It is determined whether or not vehicle 1 is likely to depart fromthe traveling lane. When there is likelihood of lane departure, an alarmis outputted from an output device 15. This function is realized by lanedeparture warning section 140 (refer to FIG. 2) which will be describedlater.

Although not illustrated, engine ECU 10, power transmission ECU 11, andtravel control device 100 include, for example, a Central ProcessingUnit (CPU), a storage medium such as a Read Only Memory (ROM) storing acontrol program, a working memory such as a Random Access Memory (RAM),and a communication circuit, respectively. In this case, for example,the function of each part (refer to FIG. 2) constituting travel controldevice 100 is realized by the CPU executing the control program. Notethat all or part of engine ECU 10, power transmission ECU 11, and travelcontrol device 100 may be integrally formed.

<Configuration Example of Travel Control Device 100>

Next, the configuration of travel control device 100 will be describedwith reference to FIG. 2. FIG. 2 is a block diagram showing an exampleof the configuration of travel control device 100.

As illustrated in FIG. 2, travel control device 100 includes roaddetermination section 110, travel control section 120, switching controlsection 130, and lane departure warning section 140. The respectiveparts will be described below.

First, lane departure warning section 140 will be described.

Lane departure warning section 140 includes image processing section141, lane detection section 142, lane departure determination section143, and alarm output processing section 144.

Image processing section 141 receives a captured image (an imageobtained by photographing the surroundings of vehicle 1) from imagingdevice 24, and performs image processing such as edge extraction on thecaptured image.

Lane detection section 142 detects a traveling lane from the imagesubjected to the image processing by image processing section 141.

Lane departure determination section 143 determines whether or notvehicle 1 is likely to depart from the traveling lane. When it isdetermined that vehicle 1 is likely to depart from the traveling lane,lane departure determination section 143 notifies alarm outputprocessing section 144, travel control section 120, and switchingcontrol section 130 of the determination.

When it is determined that vehicle 1 is likely to depart from thetraveling lane by lane departure determination section 143, alarm outputprocessing section 25 outputs an alarm from output device 15. The outputof the alarm may be, for example, a warning message display or an alarmsound (which may be a warning message).

Next, road determination section 110 will be described.

Based on the road information, road determination section 110 determineswhether or not road on which vehicle 1 travels is a predetermined road,and outputs the determination result information indicating the resultof the determination to travel control section 120. The predeterminedroad is a road on which vehicle 1 can be N coasting, and is, forexample, a road including a downhill.

The predetermined road includes a first road including a downhill suchthat vehicle 1 is accelerated, and a second road including a downhillsuch that vehicle 1 is decelerated. An example of the first road isillustrated in FIG. 3, and an example of the second road is illustratedin FIG. 4.

First road 211 illustrated in FIG. 3 is a road including a downhill suchthat gradient resistance Fs of the slope is smaller than the sum of airresistance Fa for vehicle 1 and rolling resistance Fr for vehicle 1.

In the case where vehicle 1 is N coasting during the period fromposition L1 to position L2 on first road 211, as indicated by solid line212 in FIG. 3, vehicle 1 travels while gradually increasing the velocityin a downhill portion (between position Lt and position L2).

In this way, when vehicle 1 is N coasting from position L1 to positionL2, fuel is not injected during the N coasting, so that fuel consumptioncan be improved. On the other hand, when vehicle 1 travels at constantvelocity from position L1 to position L2 (see broken line 213), fuelcontinues to be injected during the constant velocity traveling.

Second road 221 illustrated in FIG. 4 is a road including a gentledownhill such that gradient resistance Fs becomes larger than the sum ofair resistance Fa and rolling resistance Fr.

In the case of second road 221, vehicle 1 is decelerated even when thevehicle is downhill. Therefore, as illustrated in FIG. 4, when thevelocity of vehicle 1 becomes equal to or lower than maximum velocityV+V1 in a velocity higher than maximum velocity V+V1 in thepredetermined range (when vehicle 1 reaches position L3), vehicle 1starts the N coasting.

When vehicle 1 travels at constant velocity between position L3 andposition L4 in FIG. 4, the velocity of vehicle 1 is controlled to matchtarget vehicle velocity V, so that the deceleration amount in timebecomes relatively large (refer to broken line 223). On the other hand,when vehicle 1 is N coasting from position L3 to position L4 in FIG. 4,the velocity of vehicle 1 gradually decreases due to inertia force, sothat the temporal deceleration amount of vehicle 1 can be reduced morethan that at the time of constant velocity traveling (see solid line222). Therefore, the time until the velocity of vehicle 1 departs from apredetermined range can be prolonged, so that the fuel can be savedcorrespondingly.

The predetermined range described above is a range of a velocity setbased on target vehicle velocity V, and is set such that the maximumvelocity is V+V1 and the minimum velocity is V−V1, for example, based onthe setting information described above. That is, from the V+V1 (firstvelocity) larger than target vehicle velocity V to V+V1 (secondvelocity) smaller than target vehicle velocity V is set as apredetermined range. The setting of the predetermined range is performedby travel control section 120.

Road determination section 110 has been described above. In the presentembodiment, road determination section 110 is included in travel controldevice 100, but road determination section 110 may be provided outsidetravel control device 100 (including the outside of vehicle 1).

Next, travel control section 120 will be described.

Travel control section 120 recognizes whether or not the road is apredetermined road on the basis of the determination result informationfrom road determination section 110.

Further, travel control section 120 generates a traveling scheduleincluding a constant velocity traveling and an N coasting, and drivesvehicle 1 according to the generated traveling schedule based on thecurrent position of vehicle 1.

For example, at the time of constant velocity traveling, travel controlsection 120 controls the fuel injection amount of engine 3 via powertransmission ECU 11 to thereby realize traveling at a velocity accordingto the traveling schedule. For example, when the vehicle is N coasting,travel control section 120 disconnects clutch 4 via power transmissionECU 11. Further, for example, travel control section 120 controls therespective parts of braking device 40 to stop vehicle 1. The details ofthe traveling schedule will be described later with reference to FIGS. 3and 4.

In addition, travel control section 120 performs control to switch thetraveling state of vehicle 1 to either the constant velocity travelingor the N coasting in the generated traveling schedule. In other words,travel control section 120 executes either constant velocity travelingcontrol or N coasting control based on the generated traveling schedule.

Specifically, when the road on which vehicle 1 travels is apredetermined road and the velocity of vehicle 1 acquired from vehiclevelocity sensor 35 is within a predetermined range (for example, therange of V−V1 to V+V1 illustrated in FIG. 3 and FIG. 4) (that is, whenthe N coasting starting condition is satisfied), travel control section120 switches from the constant velocity traveling control to the Ncoasting control. Thus, vehicle 1 is switched from the constant velocitytraveling to the N coasting.

On the other hand, when the velocity of vehicle 1 falls outside thepredetermined range during N coasting, travel control section 120switches from the N coasting control to the constant velocity travelingcontrol. At this time, travel control section 120 controls the vehiclevelocity of vehicle 1 which is outside the predetermined range to berestored to target vehicle velocity V. Thus, vehicle 1 is switched fromthe N coasting to the constant velocity traveling.

In this manner, travel control section 120 of the present embodiment canswitch and execute the constant velocity traveling control and the Ncoasting control.

Further, travel control section 120 outputs the traveling modeinformation indicating either the constant velocity traveling control orthe N coasting control is being executed (in other words, whethervehicle 1 is traveling at constant velocity or during N coasting)appropriately to switching control section 130.

Further, when travel control section 120 receives the instructioninformation (details will be described later) from switching controlsection 130 under the N coasting control or the constant velocitytraveling control, travel control section 120 is controlled based on theinstruction information. Details will be described later.

Travel control section 120 has been described above.

Next, a description will be given of switching control section 130.Hereinafter, the operation of travel control section 120 controlled byswitching control section 130 will be described.

Switching control section 130 recognizes which of the constant velocitytraveling control and the N coasting control is being executed based onthe traveling mode information from travel control section 120.

When lane departure determination section 143 determines that vehicle 1is likely to depart from the traveling lane under the N coasting controlor the constant velocity traveling control, switching control section130 outputs the instruction information to travel control section 120.The instruction information is information indicating an instruction toprohibit the execution of the N coasting control for a predeterminedtime. The predetermined time is a time required for the brake tooperate.

First, a case where travel control section 120 receives instructioninformation under the N coasting control will be described.

In this case, based on the instruction information, travel controlsection 120 stops the execution of the N coasting control until thepredetermined time elapses from the time when it is determined thatvehicle 1 is likely to depart from the traveling lane, and executes theconstant velocity traveling control. As a result, the brake (brakingdevice 40) is enabled to operate.

If the N coasting starting condition is satisfied when the predeterminedtime has elapsed, travel control section 120 switches from the constantvelocity traveling control to the N coasting control. On the other hand,if the N coasting starting condition is not satisfied when thepredetermined time has elapsed, travel control section 120 continues thetraveling of the constant velocity traveling control.

Next, a description will be given of a case where travel control section120 receives instruction information under constant velocity travelingcontrol.

In this case, travel control section 120 does not switch to the Ncoasting control even if the N coasting starting condition is satisfieduntil the predetermined time elapses from the point in time when it isdetermined that vehicle 1 is likely to depart from the traveling lanebased on the instruction information. Therefore, travel control section120 continues execution of constant velocity traveling control duringthe predetermined time period. As a result, the brake (braking device40) is continuously operated.

If the N coasting starting condition is satisfied when the predeterminedtime has elapsed, travel control section 120 switches from the constantvelocity traveling control to the N coasting control. On the other hand,if the N coasting starting condition is not satisfied when thepredetermined time has elapsed, travel control section 120 continues thetraveling of the constant velocity traveling control.

Switching control section 130 has been described above.

<Example of a Traveling Schedule>

Next, an example of a traveling schedule used by travel control section120 will be described in detail with reference to FIG. 3 and FIG. 4.FIG. 3 is a diagram illustrating an example of road gradient informationand a traveling schedule on a first road. FIG. 4 is a diagramillustrating an example of road gradient information and a travelingschedule on a second road.

For example, travel control section 120 sequentially generates atraveling schedule corresponding to a predetermined length of time fromthe current time or a predetermined travel distance from the currentposition of vehicle 1 at regular intervals.

First, an example of a traveling schedule on the first road including adownhill such that vehicle 1 is increased in velocity will be described.

Such a traveling schedule is generated, for example, so that the movingaverage velocity is the target vehicle velocity V, the allowable maximumvelocity in the N coasting is Vmax=V+V1 or less, and the travelingcondition that the allowable minimum velocity in the N coasting is equalto or larger than Vmin=V−V1 is satisfied.

Travel control section 120 generates a traveling schedule for activelyperforming the N coasting on the basis of the road gradient information.Further, on condition that the velocity of vehicle 1 is equal to orhigher than the allowable minimum velocity Vmin at the top positionwhere the road turns from the uphill side to the downhill side, travelcontrol section 120 creates a traveling schedule including the contentsto switch from the constant velocity traveling to the N coasting beforethe top position.

As illustrated in FIG. 3, the road gradient information includes, forexample, information indicating the road altitude for each horizontaldistance (route) from current position L0 of vehicle 1, as indicated bysolid line 211 in FIG. 3. It is also possible to replace the horizontaldistance from current position L0 of vehicle 1 with the elapsed timefrom the current time. Further, the road altitude may be replaced with aroad gradient based on the relationship between the road altitude andthe front and rear road altitudes. The road gradient information ofsolid line 211 indicates that current position L0 of vehicle 1 is on theuphill side, and that a downhill slope is present immediately after theuphill slope.

For example, based on the road gradient information, travel controlsection 120 sequentially determines whether or not there is a portion(the top of the slope) that turns from the uphill side to the downhillside within a predetermined distance in front of the road.

When the top of the slope is present, travel control section 120determines whether or not the vehicle travels over the top of the hillwhile the vehicle is kept at the N coasting, when the vehicle isswitched to the N coasting at position L1 immediately after currentposition L0. That is, travel control section 120 calculates whether ornot the velocity at the top of the slope is equal to or higher thanallowable minimum velocity Vmin. Travel control section 120 performssuch calculation based on current velocity V0, the traveling resistancecoefficient of vehicle 1 obtained in advance by experiment or the like,and road gradient information.

When the vehicle is switched to the N coasting on the uphill side, thevelocity of vehicle 1 is abruptly reduced. However, in the case wherethe velocity is high or the distance to the top is short enough tomaintain the velocity at which a velocity equal to or higher than(V−V1), which corresponds to the allowable minimum velocity Vmin at aposition getting into the downhill, it is possible to satisfy theaforementioned traveling condition in which the minimum velocity in theN coasting is equal to or greater than the minimum allowable velocityVmin even if the vehicle is switched to the N coasting on the uphill.

When it is determined that the vehicle can travel over the top of thehill in a state of the N coasting, travel control section 120, forexample, switches to the N coasting at the immediately followingposition L1, and determines that the N coasting is maintained atposition L2 at which the velocity departs from the range from allowableminimum velocity Vmin to allowable maximum velocity Vmax, that is, from(V−V1) to (V+V1). Then, as indicated by solid line 212 in the lower sideof FIG. 3, travel control section 120 creates a traveling schedulehaving a content in which traveling is switched to the N coasting atposition L1, and the N coasting is maintained to position L2.

Specifically, travel control section 120 calculates an estimated value(hereinafter referred to as “top estimation vehicle velocity”) Vt of thevelocity at top position Lt when vehicle 1 performs the N coasting totop position Lt by using the following expression (1), for example.

$\begin{matrix}\left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack & \; \\{{Vt} = \sqrt{\frac{2}{M}\left\{ {{\frac{1}{2}{MV}\; 0^{2}} + {{Mgh}\; 0} - \left( {{Mght} + {{\lambda \cdot V}\;{0^{2} \cdot g \cdot \frac{\Delta\; x}{\cos\;\theta}}} + {{\mu \cdot {Mg} \cdot \Delta}\; x}} \right)} \right\}}} & (1)\end{matrix}$

Here, M is the current vehicle weight of vehicle 1, g is gravityacceleration, h0 is the altitude of current position L0 of vehicle 1, htis the altitude of top position Lt, μ, is the rolling resistancecoefficient of vehicle 1, Δx is the distance in the horizontal directionfrom current position L0 to top position Lt (route), θ is the averagegradient of a portion where vehicle 1 performs the N coasting, and V0 isa velocity of vehicle 1.

When calculated top estimated vehicle velocity Vt is equal to or higherthan the set allowable minimum velocity Vmin, travel control section 120maintains the vehicle as is when the vehicle is during N coasting anddetermines to switch the vehicle to the N coasting state when thevehicle is traveling at the constant velocity. That is, travel controlsection 120 creates a traveling schedule as indicated by solid line 212in FIG. 3, for example, and controls vehicle 1 according to thetraveling schedule.

The traveling schedule including the interval of the N coastingdetermined based on the road gradient information effectively improvesthe fuel efficiency of vehicle 1. Further, by traveling vehicle 1according to the traveling schedule, it is not necessary for the driverto perform a sequential accelerator operation.

As described above, an example of a traveling schedule on the first roadhas been described.

Next, a description will be given of a traveling schedule on the secondroad including a downhill on which vehicle 1 is decelerated.

Such a traveling schedule is generated, for example, so that theallowable maximum velocity in the N coasting is equal to or less thanVmax=V+V1, and that the allowable minimum velocity in the N coasting isequal to or greater than Vmin=V.

Based on road information, travel control section 120 creates atraveling schedule including the content of switching traveling from theconstant velocity traveling to the N coasting after the road has changedfrom a steep downhill to a gentle downhill, on condition that thevelocity is equal to or lower than the permissible maximum velocity Vmaxand equal to or higher than the allowable minimum velocity Vmin.

As illustrated in FIG. 4, the road gradient information includes, forexample, information indicating the road altitude for each horizontaldistance (route) from current position L0 of vehicle 1, as indicated bysolid line 221 on the upper side in FIG. 4. The road gradientinformation of solid line 221 indicates that current position L0 ofvehicle 1 is on the middle of the steep downhill, and position L3 is aportion changing from the steep downhill downward to the gentledownhill.

Based on the road gradient information, travel control section 120sequentially determines whether or not there is a portion that turnsfrom a steep downhill to a gentle downhill within a predetermineddistance range in front of the road. When that part is present, travelcontrol section 120 determines whether or not the velocity is within therange from V+V1 to V in a portion changing to the gentle downhill orafter changing to a gentle downhill. When the velocity is within thisrange, travel control section 120 switches from the constant velocitytraveling to the N coasting at position L3 of changing from the steepdownhill to a gentle downhill, or after position L3 where the velocitybecomes equal to or lower than V+V1 (see the solid line 222).

As indicated by solid line 222 in FIG. 4, travel control section 120creates a traveling schedule having a content in which the N coasting ismaintained from position L3 to position L4 at which the allowableminimum velocity V is achieved after the switching to the N coasting.

As a result, the velocity of vehicle 1 is decelerated, but when comparedwith the velocity at the constant velocity traveling, since thedeceleration amount is small, the time until the velocity reaches V,which is the minimum velocity, becomes longer correspondingly. That is,since the time of the N coasting can be prolonged, the fuel efficiencybetween the N coasting times is improved.

As described above, an example of a traveling schedule on the secondroad has been described.

<Operation Example of Travel Control Device 100>

Next, the operation of travel control device 100 (operation forcontrolling the traveling of vehicle 1, which is also referred to as atravel control operation hereinafter) will be described. FIG. 5 is aflowchart illustrating an example of the operation of travel controldevice 100. The flow illustrated in FIG. 5 is performed, for example,during traveling of vehicle 1 at a constant velocity or during Ncoasting of vehicle 1. The flow illustrated in FIG. 5 is repeatedlycarried out during traveling of vehicle 1.

First, lane departure determination section 143 determines whether ornot vehicle 1 is likely to depart from the traveling lane (hereinafter,referred to as likelihood of lane departure) (step S101).

If there is no likelihood of lane departure (step S101: NO) as a resultof the determination in step S101, the process returns to step S101. Inthis case, switching control section 130 does not output the instructioninformation to travel control section 120.

On the other hand, when there is likelihood of lane departure (stepS101: YES) as a result of the determination in step S101, the processproceeds to step S102.

Next, switching control section 130 outputs the instruction informationto travel control section 120 (step S102). Travel control section 120receives the instruction information.

Next, based on the instruction information, travel control section 120does not execute the N coasting control but executes the constantvelocity traveling control for a predetermined time from a time pointwhen lane departure determination section 143 determines that there islikelihood of the lane departure (step S103).

For example, when travel control section 120 receives the instructioninformation under the N coasting control, travel control section 120stops the N coasting control and executes the constant velocitytraveling control for a predetermined time period. As a result, brakingdevice 40 of vehicle 1 is enabled to operate.

For example, when the instruction information is received under theconstant velocity traveling control, travel control section 120 does notexecute the N coasting control for a predetermined time and continuesthe constant velocity traveling control even if the N coasting startingcondition is satisfied. Accordingly, braking device 40 of vehicle 1continues to operate.

The control in step S103 is performed until a predetermined time haselapsed. That is, when the predetermined time has not elapsed (stepS104: NO), the process returns to step S103. On the other hand, when thepredetermined time has elapsed (step S104: YES), the process proceeds tostep S105.

Next, travel control section 120 determines whether the N coastingstarting condition is satisfied (step S105). For example, when the roadon which vehicle 1 travels is a predetermined road and the velocity ofvehicle 1 is within a predetermined range, travel control section 120determines that the N coasting starting condition is satisfied.

When the N coasting starting condition is satisfied as a result of thedetermination in step S105 (step S105: YES), travel control section 120executes the N coasting control (step S106). Thus, vehicle 1 starts theN coasting.

In contrast, when the N coasting starting condition is not satisfied asa result of the determination in step S105 (step S105: NO), travelcontrol section 120 executes (continues) the constant velocity travelingcontrol (step S107). Thus, vehicle 1 executes (continues) constantvelocity traveling.

An example of the operation of travel control device 100 has beendescribed above.

As described in detail thus far, the present embodiment is characterizedin that in the case where vehicle 1 is likely to depart from thetraveling lane during N coasting or during traveling at a constantvelocity, the constant velocity traveling control is executed withoutexecuting the N coasting control.

Therefore, the present embodiment is capable of solving the problem thatthe N coasting is continued when vehicle 1 is likely to depart from thetraveling lane during N coasting, and thus braking device 40 is notoperated. In addition, the present embodiment is capable of solving theproblem that when vehicle 1 is likely to depart from the traveling laneduring traveling at a constant velocity, the N coasting startingcondition is satisfied and thus the N coasting is started, and as aresult, braking device 40 is not operated. Therefore, according to thepresent embodiment, safety can be secured when vehicle 1 is likely todepart from the traveling lane during N coasting or during traveling ata constant velocity.

(Variations)

It should be noted that the above embodiment is merely an example of theimplementation of this disclosure, and is not intended to limit thescope of this disclosure. That is, this disclosure may be embodied invarious forms without departing from the spirit or essentialcharacteristics thereof. Hereinafter, each variation will be described.

(Variation 1)

In the embodiment, a case where lane departure warning section 140determines whether or not vehicle 1 is likely to depart from thetraveling lane, and if there is likelihood of departure, output device15 is caused to output an alarm has been described as an example.However, the present invention is not limited thereto. For example, lanedeparture warning section 140 may determine whether or not vehicle 1 hasdeparted from the traveling lane, and if departed, output an alarm tooutput device 15. In this case, switching control section 130 may outputinstruction information to travel control section 120 when lanedeparture warning section 140 (lane departure determination section 143)has determined that vehicle 1 has departed from the travel lane.

(Variation 2)

In the embodiment, a case where lane departure warning section 140 isincluded in travel control device 100 has been described as an example,but lane departure warning section 140 may be provided outside travelcontrol device 100.

(Variation 3)

In the embodiment, switching control section 130 controls travel controlsection 120 to execute constant velocity traveling control withoutexecuting coasting control until a predetermined time elapses from apoint in time when it is determined that vehicle 1 is likely to departfrom the traveling lane, but this disclosure is not limited thereto. Forexample, switching control section 130 may control travel controlsection 120 to execute constant velocity traveling control withoutexecuting coasting control until a predetermined time elapses from thetime when an alarm is output.

<Summary of Disclosure>

The travel control device of this disclosure includes a travel controlsection that switches between constant velocity traveling control forcausing a vehicle to travel at a target vehicle velocity and coastingcontrol for allowing the vehicle to travel by inertia, and a switchingcontrol section that controls the travel control section to execute theconstant velocity traveling control without executing the coastingcontrol when the vehicle is likely to depart from the traveling laneunder the constant velocity traveling control or the coasting control.

In the travel control device, the switching control section may controlthe travel control section to execute the constant velocity travelingcontrol without executing the coasting control until a predeterminedtime elapses from a point at which it is determined that the vehicle islikely to depart from the traveling lane or a point at which an alarmfor notifying the likelihood of departure from the traveling lane isoutput.

In the travel control device, the travel control section may determinewhether or not the coasting starting condition is satisfied when thepredetermined time elapses, and if the starting condition for coastingis satisfied, terminates the constant velocity traveling control andstarts execution of the coasting control, and if the starting conditionis not satisfied, may continue execution of the constant velocitytraveling control when the starting condition for coasting is notsatisfied.

In the travel control device, the travel control section may determinethat the starting condition of the coasting is satisfied when the roadon which the vehicle travels is a predetermined road on which thevehicle is allowed to travel by inertia, and the velocity of the vehicleis within a predetermined range.

The travel control device may further include a road determinationsection that determines whether or not the road is the predeterminedroad.

The travel control device may further include: an image processingsection that performs image processing on a captured image ofsurroundings of the vehicle; a lane detection section that detects atraveling lane from the image subjected to the image processing; a lanedeparture determination section that determines whether or not thevehicle is likely to depart from the traveling lane; and an alarm outputprocessing section that causes a predetermined output device to outputan alarm for notifying the likelihood of departure from the travelinglane when the lane departure determination section determines that thevehicle is likely to depart from the traveling lane.

The vehicle of this disclosure includes a travel control device of thisdisclosure.

The travel control method of this disclosure is a travel control methodof a travel control device that switches between a constant velocitytraveling control for causing a vehicle to travel at a target vehiclevelocity and a coasting control for allowing the vehicle to travel byinertia to be executed, including executing the constant velocitytraveling control without executing the coasting control when thevehicle is likely to depart from the traveling lane under the constantvelocity traveling control or the coasting control.

This application is based on Japanese Patent Application No.2017-056555, filed on Mar. 22, 2017, the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

This disclosure is useful for a travel control device for controllingthe travel of a vehicle, a vehicle, and a travel control method.

REFERENCE SIGNS LIST

-   1 vehicle-   2 automatic traveling device-   3 engine-   4 clutch-   5 transmission-   6 propulsion shaft-   7 differential device-   8 drive shaft-   9 wheel-   10 engine ECU-   11 power transmission ECU-   13 target vehicle velocity setting device-   14 increase/decrease value setting device-   15 output device-   20 road information acquisition device-   21 current position acquisition device-   22 weather acquisition device-   23 ambient sensor-   24 imaging device-   30 vehicle information acquisition device-   31 accelerator sensor-   32 brake switch-   33 shift lever-   34 turn signal switch-   35 vehicle velocity sensor-   40 braking device-   41 foot brake-   42 retarder-   43 exhaust brake-   100 travel control device-   110 road determination section-   120 travel control section-   130 switching control section-   140 lane departure warning section-   141 image processing section-   142 lane detection section-   143 lane departure determination section-   144 alarm output processing section

What is claimed is:
 1. A travel control device, comprising: a travelcontrol circuitry that switches between a constant velocity travelingcontrol for causing a vehicle to travel at a target vehicle velocity anda coasting control for allowing the vehicle to travel by inertia in astate where a clutch is disengaged and an engine is disconnected fromwheels, switching from the constant velocity traveling control to thecoasting control being performed when the velocity of vehicle is withina predetermined range, and a switching control circuitry that controlsthe travel control circuitry to execute continuing the constant velocitytraveling control without executing the coasting control even when thevelocity of vehicle is within the predetermined range, when the vehicleapproaches within a predetermined distance to a boundary of a travelinglane under the constant velocity traveling control, and executeswitching to the constant velocity traveling control without executingthe coasting control even when the velocity of vehicle is within thepredetermined range, when the vehicle approaches within thepredetermined distance to the boundary of the traveling lane under thecoasting control.
 2. The travel control device according to claim 1,wherein the switching control circuitry controls the travel controlcircuitry to execute the constant velocity traveling control withoutexecuting the coasting control even when the velocity of vehicle iswithin the predetermined range until a predetermined time elapses from apoint at which it is determined that the vehicle approaches within thepredetermined distance to the boundary of the traveling lane or a pointat which an alarm for notification of approaching within thepredetermined distance to the boundary of the traveling lane is output.3. The travel control device according to claim 2, wherein the travelcontrol circuitry determines whether or not a starting condition of thecoasting is satisfied when the predetermined time has elapsed, when thestarting condition of the coasting is satisfied, the travel controlcircuitry terminates the constant velocity traveling control and startsexecution of the coasting control, and when the starting condition ofthe coasting is not satisfied, the travel control circuitry continues toexecute the constant velocity traveling control.
 4. The travel controldevice according to claim 3, wherein the travel control circuitrydetermines that the starting condition of the coasting is satisfied whenthe road on which the vehicle travels is a predetermined road on whichthe vehicle is allowed to travel by inertia, and a velocity of thevehicle is within a predetermined range.
 5. The travel control deviceaccording to claim 4, further comprising a road determination circuitrythat determines whether or not the road is the predetermined road. 6.The travel control device according to claim 1, further comprising: animage processing circuitry that performs image processing on a capturedimage of surroundings of the vehicle; a lane detection circuitry thatdetects the boundary of the traveling lane from the image subjected tothe image processing; a lane departure determination circuitry thatdetermines whether or not the vehicle approaches within thepredetermined distance to the boundary of is likely to depart from thetraveling lane; and an alarm output processing circuitry that, when thelane departure determination circuitry determines that the vehicleapproaches the predetermined distance to the boundary of is likely todepart from the traveling lane, causes a predetermined output device tooutput an alarm to notify the approach of the predetermined distance tothe boundary of the traveling lane.
 7. A vehicle, comprising: a travelcontrol device comprises a travel control circuitry that switchesbetween a constant velocity traveling control for causing a vehicle totravel at a target vehicle velocity and a coasting control for allowingthe vehicle to travel by inertia in a state where a clutch is disengagedand an engine is disconnected from wheels, switching from the constantvelocity traveling control to the coasting control being performed whenthe velocity of vehicle is within a predetermined range, and a switchingcontrol circuitry that controls the travel control circuitry to executecontinuing the constant velocity traveling control without executing thecoasting control even when the velocity of vehicle is within thepredetermined range, when the vehicle approaches within a predetermineddistance to a boundary of a traveling lane under the constant velocitytraveling control, and execute switching to the constant velocitytraveling control without executing the coasting control even when thevelocity of vehicle is within the predetermined range, when the vehicleapproaches within the predetermined distance to the boundary of thetraveling lane under the coasting control.
 8. A travel control methodperformed by a travel control device that switches between a constantvelocity traveling control for causing a vehicle to travel at a targetvehicle velocity and a coasting control for allowing the vehicle totravel by inertia in a state where a clutch is disengaged and an engineis disconnected from wheels, switching from the constant velocitytraveling control to the coasting control being performed when thevelocity of vehicle is within a predetermined range, the methodcomprising: executing continuing the constant velocity traveling controlwithout executing the coasting control even when the velocity of vehicleis within the predetermined range, when the vehicle approaches within apredetermined distance to a boundary of the traveling lane under theconstant velocity traveling control, and executing switching to theconstant velocity traveling control without executing the coastingcontrol even when the velocity of vehicle is within the predeterminedrange, when the vehicle approaches within the predetermined distance tothe boundary of the traveling lane under the coasting control.
 9. Thetravel control device according to claim 1, wherein the travel controlcircuitry switches from the coasting control to the constant velocitytraveling control when the velocity of vehicle is outside thepredetermined range.
 10. The travel control device according to claim 1,wherein the predetermined range is set from a first velocity greaterthan the target vehicle velocity to a second velocity less than thetarget vehicle velocity.
 11. The travel control device according toclaim 1, wherein the travel control circuitry generates a drivingschedule that includes a constant velocity traveling and a coastingbased on road information, and switches between the constant velocitytraveling control and the coasting control based on the drivingschedule.